Re: Wireless antenna setup

homie.6 <homie.6.30be4c@no-mx.wirelessforums.org> wrote in
news:homie.6.30be4c@no-mx.wirelessforums.org:

>
> I recently purchased a Dlink Wireless Airplus G Pci Card 2.4Ghz and a
> Yagi 14db antenna. I mounted the antenna on the roof with a relatively
> clear shot to my friends house . I'm also using lmr-400 cable. The card
> is setup correctly because I pickup my neighbor with the little stubby
> the card comes with. I have the antenna and cable to reach my friend.
> When I screwed in the new cable my reception was no better with the
> expensive antenna and cabling over the stub. Can anyone answer what am
I
> skipping .:(

bi24 was right about antenna aiming, but not about the 1-watt amp. You
don't want to use a 1-watt amp. The largest antenna you can use with a 1-
watt amp would be 6 dBi, legally. But you would end up with a receive
path with 8dB less gain. Typically, you would want to use the highest
gain antenna you can and still stay under the 36 dBm ERP limit.

LMR-400 is 6.8 dB/100 ft. Looking at a 100 foot run to make it easy.
Since the card is 15 dBm (nominally), and a 100 ft cable run....

15 dBm (TX power) - 6.8 dB (cable loss) + 14 dbi (ant gain) = 22.2 dbm
ERP.

Well below the 36 dBm limit. So in this case, you would be allowed to use
a 28'ish dBi antenna. This would give a 14 dB gain (over the original 14
db) on the RX side, while still maintaining a 36 dBm ERP level.

Here is a Operating margin calculator. You need to know the operating
specs of both ends (TX power/cable loss/antenna gain/RX sensitivity).
Note that quick calculators like this are dealing with an ideal world,
and you described your location as a 'relatively clear shot', whatever
that means.....

http://www.simrex.com/site/tools/som.php4

Also keep in mind that tools like this are also intended for 'fixed'
wireless, not mobile.

I'd look at aiming, as was said, and antenna location. Moving the antenna
a couple feet this way or a couple feet that way can make a significant
difference. And be sure the cable length is as short as possible.

At the bottom of this page is a typical pattern for a 14 dBi Yagi-like
antenna.

http://www.sparcotech.com/cgi-bin/co...on&key=PC2415N